He strangled Miss Yeates after becoming obsessed with violent sex and pornography, it can now be revealed.

Videos recovered from his laptop depicted blonde women being throttled during sex.

Just two weeks before murdering the landscape architect he also paid for sex with a prostitute during a business trip to Los Angeles, police discovered.

Dutchman Tabak, 33, throttled Miss Yeates in a violent confrontation at her flat in Clifton, Bristol, on December 17 last year.

The petite blonde suffered 43 injuries during a desperate fight for life as he used his burly 6ft 4in frame to overpower her.

Miss Yeates, who did not even know her killer's name, is believed to have been dead within about 20 seconds of Tabak grabbing her neck.

For reasons only he knows, Tabak kept her sock and took a Tesco Finest pizza she had bought earlier that night as she walked home from the pub.

He then immediately launched into an elaborate chain of acts to construct an alibi and cover his tracks.

Tabak carried Miss Yeates's body in his arms back to his flat next door and put her in his bicycle bag. In a bizarre twist he then went night shopping in Asda with her in his car boot.

While wandering the aisles - picking up rock salt, crisps and beer - Tabak texted his girlfriend to say he was bored.

But in reality he was plotting the best way to dispose of Miss Yeates's body.

Within an hour he had dumped her partially-clothed body in the foetal position on a snowy verge in Failand, near Bristol.

Just 24 hours later he was drinking champagne with friends as he embarked on a life of lies that would lead police to dismiss him as a concerned neighbour.

He scoured the internet for clues to how he could get off the hook before and after her snow-covered body was found by dog walkers on Christmas Day.

It is believed he may even have been getting sexual satisfaction from looking up pictures of Miss Yeates.

Detectives who recovered his laptops found he was looking at pornographic websites within seconds of looking at pages surrounding the inquiry into the death of Miss Yeates.

In the hours, days and weeks following her death, Tabak repeatedly lied about his actions to his girlfriend, his family, police and even his legal team.

"Vincent Tabak is very clever," prosecutor Nigel Lickley QC said. "He is intelligent and highly educated. He is dishonest, he is deceitful and he is a liar.

"He is when he chooses to be very calculating. Making decisions, covering his tracks.

"There is a word for it - that is shrewd."

He accused Tabak of being "calculating" in the months after the killing - lying continuously in emails to his girlfriend and family.

But he began to slip up - changing his story over and over again as more evidence emerged as to his guilt - answering "I can't remember" more than 80 times to difficult questions during his three-week trial at Bristol Crown Court.

From the witness box he wept as he apologised to Miss Yeates's relatives for putting them through hell.

The bespectacled engineer - speaking with a shrill Dutch accent - said he would be haunted for the rest of his life "no matter what sentence I get".

But the jury failed to be swayed by Tabak's tears.

Miss Yeates and boyfriend Greg Reardon were described by friends as "the perfect couple".

On the night of her death, she had told landscape architect colleagues over Christmas drinks how she was dreading being without Mr Reardon for the weekend.

Mr Reardon, who had been visiting relatives in Sheffield, told of his rising sense of panic as he realised she had disappeared after returning to an empty flat.

A prosecution bid to include Tabak's previous sexual perversions was thrown out twice during the trial.

Mr Justice Field said it would be inappropriate for the jury to hear how he had cheated on his girlfriend Tanja Morson by paying for sex with a prostitute he had hooked up with on an escort website.

Mr Reardon maintained his composure in the public gallery as the jury foreman delivered the guilty verdict.

Miss Yeates's parents had decided not to attend court today.

Tabak looked down at his feet but showed no sign of emotion as the verdict was delivered.

He immediately sat down and put his head in his hands.

Mr Justice Field began sentencing by telling the jury: "I think there was a sexual element to this killing."

Mr Justice Field told Tabak: "You have been convicted of the murder of Joanna Yeates on sound and substantial evidence.

"When you entered her flat on the evening of December 17 last year you did not even know her name and had had virtually nothing to do with her.